ANKARA, April 18 (Xinhua) -- Turkey is not just a buyer of U.S. F-35 fighter jets but also a technology partner in the production program, Turkish presidential spokesman Ibrahim Kalin said on Thursday.

"Turkey is, and will continue to be, a partner of F-35 technology. We are not just a client or buyer of F-35s, " Kalin told reporters following a cabinet meeting in the capital Ankara.

Turkey is one of the participants in the U.S. F-35 international program, but its decision to buy the advanced Russian S-400 surface-to-air missile system has strained its relations with the U.S., which threatened to suspend the sale of F-35 jets to Turkey unless it scraps the S-400 deal.

Last week, Turkish President Recep Tayyip Erdogan reiterated that Turkey's procurement of the Russian S-400 air defense systems is a national security deal, criticizing U.S. for halting the F-35 deliveries.